Contemporary hard disk drives include an actuator assembly pivoting through an actuator pivot to position one or more read-write heads, embedded in sliders, each over a rotating disk surface. The data stored on the rotating disk surface is typically arranged in concentric tracks. To access the data of a track, a servo controller first positions the read-write head by electrically stimulating the voice coil motor, which couples through the voice coil and an actuator arm to move a head gimbal assembly in lateral positioning the slider close to the track. Once the read-write head is close to the track, the servo controller typically directs the read-write head to follow the track, and the read-write head is used to access data stored in the track.
Micro-actuators provide a second actuation stage for lateral positioning the read-write head while following the track. They often use an electrostatic effect and/or a piezoelectric effect to rapidly make fine position changes. They have doubled the bandwidth of servo controllers and are now believed essential for high capacity hard disk drives. This invention will focus on elements of a micro-actuator based upon the piezoelectric effect.
Contemporary hard disk drives fly the slider and its embedded read-write head within a few nanometers of the rotating disk surface during read and write access operations. The flying conditions are significantly affected by the local temperature and pressure. The temperature and pressure in the vicinity of the micro-actuator may vary from elsewhere in the hard disk drive. Apparatus and methods are needed to accurately estimate the temperature and/or the pressure near the slider and to operate a hard disk drive accordingly.